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CVE-2026-40360: Microsoft Excel Information Disclosure Vulnerability

• Severity: high (CVSS 7.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-05-12 · updated 2026-10-26
• Weakness: CWE-125

Description

Out-of-bounds read in Microsoft Office Excel allows an unauthorized attacker to disclose information locally.

Affected products

• Microsoft 365 Apps: all versions
• Microsoft Excel 2013 Service Pack 1: 2016
• Microsoft Office: 2019
• Microsoft Office LTSC for Mac 2021: 2021, 2024
• Microsoft Office Online Server: before 16.0.10417.20128 — fixed in 16.0.10417.20128
• Microsoft 365 Apps: from 16.0.1 before https://aka.ms/OfficeSecurityReleases — fixed in https://aka.ms/OfficeSecurityReleases
• Microsoft Excel 2016: from 16.0.0.0 before 16.0.5552.1000 — fixed in 16.0.5552.1000
• Microsoft Office LTSC 2021: from 16.0.1 before https://aka.ms/OfficeSecurityReleases — fixed in https://aka.ms/OfficeSecurityReleases
• Microsoft Office LTSC for Mac 2024: from 16.0.0 before 16.109.26051019 — fixed in 16.109.26051019
• Microsoft Office: from 19.0.0 before https://aka.ms/OfficeSecurityReleases — fixed in https://aka.ms/OfficeSecurityReleases
• Microsoft Office LTSC 2024: from 16.0.0 before https://aka.ms/OfficeSecurityReleases — fixed in https://aka.ms/OfficeSecurityReleases
• Microsoft Office LTSC for Mac 2021: from 16.0.1 before 16.109.26051019 — fixed in 16.109.26051019
• Microsoft Office Online Server: from 16.0.0.0 before 16.0.10417.20128 — fixed in 16.0.10417.20128

How to fix

Upgrade to a fixed version: Microsoft Office Online Server 16.0.10417.20128; Microsoft 365 Apps https://aka.ms/OfficeSecurityReleases; Microsoft Excel 2016 16.0.5552.1000; Microsoft Office LTSC 2021 https://aka.ms/OfficeSecurityReleases; Microsoft Office LTSC for Mac 2024 16.109.26051019; Microsoft Office https://aka.ms/OfficeSecurityReleases; Microsoft Office LTSC 2024 https://aka.ms/OfficeSecurityReleases; Microsoft Office LTSC for Mac 2021 16.109.26051019; Microsoft Office Online Server 16.0.10417.20128. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40360

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